Combination gas and oil burner and control system therefor



March 17, 1953 2,631,656

. R. H. SIEMON COMBINATION GAS AND OIL NER AND CONTROL SYSTEM THE FORFiled Oct. 11, 1948 5 Sheets-Sheet l fly 1 I 202% m 9 2r; W"

w- -{I A?! 2 Q #4 07 zm- A M d @I If? w 2% 7% Z a}? 2% 1 "C 92 w w I xfi/thy/"d T5927? March 17, 1953 R. H. SIEMON COMBINATION GAS AND OILBURNER AND CONTROL SYSTEM THEREFOR 5 Sheets-Sheet 2 Filed Oct. 11, 1948v INVENTOR, Pic/bra 176M070.

March 17, 1953 R. H. SIEMON 2,631,656

COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR Filed Oct.11, 1948 5 Sheets-Sheet 5 INVENTOR, Pithrd A? .SlWra/I.

March 17, 1953 R. H. SlEMON 2,631,656

COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR Filed Oct.11, 1948 5 Sheets-Sheet 4 March 17, 1953 2,631,656

R. H. SIEMON COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFORFiled Oct. 11, 1948 -5 Sheets-Sheet 5 JZLL" w j 1 we 1 Q 0 I J vINVENTQR,

4 Fla/9am Karma/7.

Patented Mar. 17, 1953 UNITED STATES TENT OFFICE COMBINATION GAS AND OILBURNER AND CONTROL SYSTEM THEREFOR 10 Claims.

This invention relates to new and useful improvements in automaticallycontrolled combination gas and oil burners, and relates particularly toa burner adapted to burn either gas or oil, and to switch automaticallyfrom one fuel to the other responsively to certain control conditions,such as the outdoor atmospheric temperature or the pressure in the gassupply line.

Due to the shortage of fuel gas for he t prevailing in many part of thecountry, numerous cities have conditioned permits to install householdgas heating equipment on the provision of a stand-by fuel supply such asoil, said oil to be burned during the periods of peak gas load. It istherefore the principal object of this invention to provide acombination gas and oil burner arrangement adapted to burn gas as lon asthe outside air remains above a predetermined temperature, but whichwill switch automatically to oil whenever the outside air falls belowsaid predetermined temperature, and to switch automatically back to gaswhen the outside temperature again rises above said predetermined level.Since the gas load in a gas supply system is generally inverselyproportional to the outside temperature, this control means is effectiveto turn off the gas during peak load periods.

Another object is the character described, of automatic pressuresensitive means for switching from gas to oil fuel whenever the pressurein the gas supply line falls below a predetermined level, re

less of the outside temperature.

A further object is the provision of a combination gas and oil burnersystem wherein the oil isignited by means actuated by an insidethermostat, and having means actuated by the oil flame to ignite the gasfuel and to shut off the oil burner whenever the outside temperature andthe gas pressure are above predetermined levels, and automatic means forSwitching to oil fuel whenever either the outside temperature or the gaspressure falls below said predetermined levels.

A still further object is the provision, in a combination gas and oilburner system of the character described, of independent draft means forsupplying air for combustion to said gas and oil burners, the draftmeans for said gas burner being self-regulating according to the amountof gas being burned, and being adapted to close automatically when oilis being burned.

Other objects are simplicity and economy of construction, accuracy anddependability of pthe provision, in a device of side wall l and a floorpartition 6.

oration, adaptability to include a standard untype oil burner, andadaptability to use only standard, commercially available controldevices.

With these objects in view as well as other objects which will appear inthe course of the specification, reference will be had to the drawing,wherein:

Figure 1 is a schematic layout of an automatically controlledcombination gas and oil burner system embodying the present invention.

Fig. 2 is an enlarged fragmentary section taken on line 11-11 of Fig. l,with parts left in elevation.

Fig. 3 is a fragmentary section taken on line III-III of Fig. 2, withparts left in elevation.

Fig. 4 is a fragmentary section taken on line IV-IV of Fig. 2, withparts broken away and other parts left in plan.

Fig. 5 is a fragmentary section taken on line V-'V of Fig. 4, with partsbroken away and other parts omitted.

Fig. 6 is a fragmentary section taken on line VI-VI of Fig. 5.

Fig. 7 is a. fragmentary section taken on line VII-VII of Fig. 2.

Fig. 8 is a schematic wiring diagram of the burner controls.

Fig. 9 is a schematic wiring diagram of a modified form of the burnercontrol system.

Fig. 10 is a view similar to Fig. 4, including I the principalmodifications indicated in Fig. 9.

Like reference numerals apply to similar parts throughout the severalviews, and the numeral 2 applies to a furnace shown in Fig. 1 disposedin the basement of a building having an out- Said furnace may be of anycommon type such as warm air, hot water, or steam, and is provided witha suitable stack pip 8. The combination gas and oil burner includes astandard gun-type oil burner l0, said oil burner including a blast tubel2 disposed horizontally, said blast tube extending at its inner endflush with the inner surface I of the refractory combustion chamber wallH! of furnace 2, a fan housing It carried by and interconnected withsaid blast tube adjacent the outer end thereof, a fan wheel l8 carriedin said housing and operable by a motor 20 mounted at one side of thefan housing to supply air under forced draft to blast tube l2, and anoil pump 22 mounted on the opposite side of fan housing 15 coaxiallywith motor 20, said pump also being driven by said motor throughcoupling 24, as shown in Fig. 3. Said pump is provided with a suctionline 26 and a return line 28 connecting it with a Suitable supply offuel oil. The delivery line 30 of said pump is interconnected with anoil tube 32 which passes through rear closure plate 34 of blast tube i2and extends axially through said blast tube to a point adjacent the openinner end thereof. Said oil tube carries at its inner end a nozzle 36adapted to direct a finely divided oil spray into the furnace combustionchamber. Said oil tube is supported intermediate its ends within blasttube 52 by means of spider 38, and the outer end portion of blast tubeI2 is supported by a floor-engaging leg 46.

Oil emerging from nozzle 36 is ignited by an electric spark passingacross spark gap 42 between electrodes 44 adjacent the tip of saidnozzle. Said electrodes are disposed adjacent oil tube 32, and aresupported from said oil tube by clamp 46. The electric leads 48 and 50to said electrodes pass through insulating fittings 52 providedtherefore in closure plate 34, and are respectively interconnected withthe secondary terminals of ignition transformer 54, which is carried ina suitable housin mounted on fan housing I6.

'As best shown in Figs. 2, 3 and '7, a burner box 56 of sheet metalconstruction is disposed about the inner end portion of blast tube I2.Said box is substantially rectangular in transverse crosssection, andcomprises a top wall 58, bottom wall 80, side walls 52 and 64, an outerend wall 66, and an inner end wall 58 flush with the inner surface offurnace wall i i and extending from the upper edge of box 56 to a pointspaced apart from the lower edge thereof, as best shown in Fig. 5. Anopen-ended tube It extends horizontally between outer wall 65 and innerwall 68 through the upper portion of box 56, and blast tube I2 of theoil burner extends therethrough. The space between tube lb and blasttube I2 is filled with a heat insulating material I2.

A plurality of horizontally disposed, laterally spaced apart gas burnertubes I4 are carried in' the lower portion of burner box 58 parallel toblast tube I2, being secured rigidly to brackets "I6 extending betweenand fixed to side walls 32 and 6 tubes are flush with the inner surfaceof furnace wall I4 and beneath the lower edge of inner wall 68, and theouter ends of said tubes are fitted with apertured plates 58 which serveto center therein coaxially disposed pipe nipples 80, to the inner endsof which are carried nozzles 32, so disposed that when gas is suppliedto said nozzles through said nipples, air will be drawn into tubes I4through apertured plates I8 and intermixed with said gas. Pipe nipples80 are externally threaded to receive thereon closure discs 84, whichmay be moved adjustably to and from the ends of tubes M to regulate theamount of air entering said tubes. All air which does not enter tubes I4will pass around the outside of said tubes and be intermixed with theburning air-gas mixture emerging from the inner ends of said tubes,thereby providing a secondary supply of air for complete combustion. Theouter ends of nipples 80 are interconnected with a common transverseheader pipe 86. Said header is mounted on a bracket 88 fixed to bottom60 of box 56, extends outwardly through side wall 64 of said box, and isinterconnected at its outer end with a gas supply pipe 94].

The lower portion of burner box 56 is extended outwardly from the upperportion thereof, and is The open inner ends of said gas burner providedat its outer end with a damper door 92 hinged at 94, and. adaptednormally to be retained closed by gravity. Said damper is operated by apressure sensitive damper control 96 disposed in gas supply line 9%. Asbest shown in Fig. 6, said damper control comprises a housing 98carrying a flexible diaphragm IE5 beneath which gas from pipe is adaptedto enter. A lever N2 is pivoted adjacent one endto housing 98 at I04,and is pivotally connected at we intermediate its ends to a slide rodIE3 fixed to and operable by diaphragm Hit. The free end of lever 452 isconnected by chain His with a pin II2 fixed to the free edge of damperdoor 92. Thus whenever there is gas pressure in gas supply line 86, thedamper will be opened, and the amount it is opened will be proportionalto the gas pressure. Hence the damper is automatically regulated and byselecting a damper control of the proper sensitivity, and by adjustingthe length of chain III), damper 92 will open suihciently to permit theamount of air required for proper combustion of the gas being burned.

A solenoid operated gas valve 5 I4 is inserted in gas supply line 90behind damper control 96, and a pilot gas tube H3 is interconnected withsaid supply line behind said main valve, said connection usually beingmade within the body of valve iI i itself. Said pilot tube is providedwith a solenoid operated valve i !8, enters burner box 56 immediatelybeneath header 8t, and extends transversely beneath the inner ends ofgas burner tubes M. That portion of said pilot tube adjacent the forwardends of the gas burner tubes is provided with a plurality oflongitudinally spaced apertures I20. The gas escaping from saidapertures is ignited by the flame of the oil burner as hereinafterdescribed.

Within burner box 56, pilot tube I I 3 is provided with a branch tubeI22 adapted to supply gas to a flame actuated switch device I24 bestshown in Figs. 5 and 8. Said device is disposed in the upper portion ofburner box 56 adjacent tube It, andcomprises a tube I25 fixed in outerwall 65 of said burner box and extending to a point adjacent the innerwall G8 thereof, a horseshoe shaped bimetallic element I26 fixed at oneend to the inner end of said tube and fixed at its opposite end to oneend of a rod I23 disposed within tube I25, and an electric switch 33%carried in a housing I32 disposed outside of burner box 56 and operableby the movement of rod E28. As shown in Fig. 5, tube I22 supplies gas toa jet I34 adapted to apply a flame against bimetallic element I26.Switch I3fl remains open so long as no flame is applied to thebimetallic element, but closes when the flame is so applied. Inner wall68 of burner box 56 is provided with an aperture 536 adjacent bimetallicelement !26, and gas supplied to jet I34 may be ignited directly throughsaid aperture by the oil burner flame. However, in order to insurepositive ignition of the jet, an auxiliary pilot tube i38 isinterconnected at its lower end with pilot tube H6 and extends upwardlyadjacent wall 68 and across aperture 535. Said auxiliary pilot tube isprovided along its length with spaced apart holes it as shown. in Fig.5. This device is known as a ladder pilot. When gas from pilot tube H6is ignited by the oil burner, gas escaping from the lower holes I46 oftube I38 is ignited by said pilot. The flame then travels upwardly alongtube I38, successively lighting gas from the next higher hole Mil untila flame is directed inwardly through aperture I36 to ignite jet I34.

enemas 'R r i g o Fig. 8 fora-wiri g dia ram of the control system, itwill be seen that line Wires I42 and 5144 are connected by wires I48 andI48 with the primary terminalsof atrans rm r 5 suitable for stepping theline yoltage down to a level suitable for the operation of rel ys, etc.Amain switch A52 is disposed in wires I lfiand I48, and a limit ,controlIE4 is disposed in series in wire I48. Said limit control comprises anelectrical switch normally closed and adapted ,to he opened by abimetallic element L58 whenever said element is h a d abov a pr dtermine emp ratu Said bimetallic element is positioned in the furnacebonnet v{asindicated in Fig. l, and thus adapts the limit control toshut off the entire system whenever. {the bonnet temperature exceeds asafe level.

Wire I48 is connected by wire I58 with the armature of a-relay .I88,,and the fixed terminal of said relay is connected by wire 'I 82 with oilburner motor 28, and by means of wires I82 .and I64 with one of theprimary terminals of ignition transformer 54. The other primary terminalof said transformer, and the other terminal of said motor 28 areconnected with wire I48 by wires I86 andv wire I58, thus completing theoil burner circuit. Relay I88 is normally open, and hence the -,oilburner can not function except when the coil of relay 'I 68 isenergized. One of the secondary terminals of transformer 54 is connectedto said relay coil by wire I18, and the other wire I72 fromsaid coil isconnected with the armature of normally open relay H4. The othersecondary terminal of transformer I58 is connected by wire I18 with amovable switch member of stack switch I18. Said movable switch member isoperable by a bimetallic member I88 disposed in the stack pipe 8 of thefurnace 2 to connect wire I'IB with either a wire I82 connected with thearmature of a relay I14, when bimetallic member I88 is heated, or with awire I84. Wire I84 is connected with a safety switch comprising inseries a heater coil I86, a bimetallic switch element I88 adapted to beheated by said heater coil, and a fixed contact I98 connected with wireI82 by wire I9I. Said safety switch is norm-ally closed when heater coilI86 is not energized. Hence when relay I14 is closed by meanshereinafter described, the secondary circuit of transformer I58 isclosed to energize relay I68, thus completing the oil burner circuitand. starting it in operation. At the beginning of furnace operation,said secondary circuit flows through safety switch I88, energizingheater coil I88. If, within a predetermined number of seconds from thebeginning of operation, stack switch I18 has not been operated by theheat of the cilcombustion products rising in stack pipe 8 to connectwire I'IIi directly with wire I82, heater coil will open switch I88,thus breaking the oil burner circuit. Safety switch I88 is retained inthe open position by a latch I 89, which must be manually released, thuspreventing starting of the oil burner till the defects therein have beencorrected. Transformer I58, relay I68, stack switch I18, and safetyswitch I88 are normally encased ina single housing and designated as therimary oil burner control I92, said control being disposed adjacentstack pipe 8 with bimetallic element I88 projecting into said stackpipe, as shown in Fig. 1.

The primary terminals of step-down transformer I94 are connected withwires I46 and I48 respectively by wires I98 and I88. One secondaryterminal of said transformer is connected by wire 288 with an insidethermostat 282, which is n efie swit h adjustab e to c ose henever the.temperaturein the building to he heatedfa ls below the desired level.The other pole of thermostat is connectedby wires 284 and 288 with thearmature of a double-throw relay 288. Said armature connectsnormallywith a wire 2 I 8 connected to the coil of relay I'l4,-and the otherterminal of said coil is connected by wire 2I2, and wire 2M with areturnwire 2 I6 to the secondary of transformer I84. Thus whenever thermostat282 is closed, calling for heat, the circuit to the coil ofrelay I14will be completed through wire 288, thermostat 282, wires 284- and 286,relay 288, wire 2I8, the coil of relay I14. and wires 2,I 2 2J4 andZ I6.Relay I'I4 will then close, actuatingthe oil burner circuit aspreviously described.

Wire 284 is connected by wire 2 I8 with an outdoor thermostat 228, whichis set to close at and above some temperature representing the period ofpeak gas load, and to open when the outside temperature falls below saidpredetermined level. It is contemplated that this thermostat should beset and sealed by the public utility authorities. The other pole of saidthermostat is connected by wire 222 with one terminal of solenoidoperated gas pilot valve II8, and return wire 2I6 is connected to theother terminal of said valve. Thus whenever thermostat 282 is closed toactuate the oil burner circuit as previously described, and the outdoortemperature is above the setting of thermostat 228, the circuitto pilotvalve IIB will be completed through wire 288, thermostat 282,

wires 284 and H8, thermostat 228, wire 22,2, valve and thence to commonreturn wire 2I8 by wire 2I4. Thus when switch I38 is closed by theaction of jet I84, the circuitto the relay of coil 2.88 is completedthrough wires 288 and 224, switch 38, wire 22E, relay 288, and wires 2I4and 218.

The armature of relay 288 thus breaks contact with wire 2I8, breakingthe circuit to relay I14 and shutting off the oil burner, andestablishes contact with wire 228, which is connected with main gasvalve I I4. The returnwire 228 of said main gas valve is connected withcommon return wire 2I8. The circuit to the main gas valve is thuscompleted through-wire 288, thermostat 282, wires 284 and 288, thearmature of relay 288, wire 228, main valve I I4, and wires 228 and 2I6.Main valve I I4 is thereby opened, permitting gas tooperate dampercontrol 96, and to flow through header 88, nipples 88, nozzles 82, andburner tubes '54, where said gas is ignited by the pilot tube I I6.

If for any reason the pilot has-failed-to ignite, the oil burner willcontinue to operate, since then flame actuated switch I38 will not beclosed to energize relay 288 to interrupt the circuit to the oil burner.If, while the gas burner is in operation, the outdoor temperature shouldfall below the setting of thermostat 228, said thermostat will hascooled sufiiciently, which requires only a few seconds, switch I38 willbe opened, thereby brealsnc t circu to he .11 o re ay 2 8.- Tifirrfllay, thus de-energized, breaks the circuit to the main gas valveH4 and reestablishes the circuit to the coil of relay I74, and saidrelay closes the circuit to the oil burner as previously described. If,while the gas burner is in operation, the pressure in the gas supplyline falls below a predetermined level, the flame at jet 34 of flameswitch mechanism I24 will become too small to actuate bimetallic memberI26, and switch I90 will open. This breaks the circuit to relay 208,which then operates to close the main gas valve and start the oil burneras described. above. This cycle will also occur in case of total gasfailure. In this instance the gas pilot will continue burning after theoil burner is lit, but this is not considered obj ectionable. If, afterthe oil burner has been put back in operation, the outside temperatureshould again rise above the level at which thermostat 220 is set, saidthermostat will again close to initiate the gas lighting cyclepreviously described. Likewise, if the oil burner has been put inoperation by low pressure or failure of the gas supply, and the pressureis again restored, jet I34 will again function to close switch I36, andrelay 208 will function to shut off the oil burner and open the main gasvalve.

.As shown in Figs. 1 and 8, relays I14 and 208, and transformer I94, maybe enclosed in a wall mounted housing 230. Line wires I46 and I48 fromswitch I52 pass to a junction box 232 through conduit 234. From saidjunction box, suitable connections are made to limit switch I54 throughconduit 236, to primary oil burner control I92 through conduit 238, andto relay and transformer housing 230 through conduit 240. From saidhousing, connections are made to the oil burner through conduit 242, andto the gas control apparatus through conduit 244. A conduit 246 extendsthrough floorpartition 6 into the rooms to be heated for connection withinside thermostat 202, and a conduit 248 extends through outside wall 4for connection with outside thermostat 220.

In the modified form of control system shown in Figs. 9 and 10,substantially similar results are obtained in a simpler manner usingfewer controls. The pilot tube II6, pilot valve IIS, flame actuatedswitch mechanism I24, and relays I14 and 208, which are present in theform shown in Figs. 1 to 8, are omitted. A pressure sensitive, diaphragmoperated electric switch 250 is inserted in gas supply line 90 betweenmain gas valve H4 and damper control 56, and an additional stack switch252 is used, said stack switch being operable by a bimetallic element254 adapted to be positioned in furnace stack pipe 8.

Referring to Fig. 9 for the wiring diagram of the modified controlsystem, it will be noted that wires I46 and I48 are connected with mainswitch I52, limit switch I54, and the primary terminals of transformerI50 of primary burner control I92 just as in the preferred form. Saidprimary burner control is identical with the control used in thepreferred form, however, the lead wires I12 and I82 of the secondarycircuit of transformer I50 are connected directly to inside thermostat202, and the line voltage lead wires I62 and I66 from said primarycontrol are connected directly to the primary terminals of gas controltransformer I94. Wire I62 is connected by wire 256 with one pole ofpressure switch 256.

The other pole of said switch is connected by wires 258 and 260 with oilburner motor and the primary of ignition transformer 54. The returnwires 262 and 264 of said motor and 8 transformer are connected withreturn Wire I66. Thus when thermostat 202 closes to complete the circuitto the coil of relay I60, said relay closes and completes the circuit tothe oil burner through wire I48, the armature of relay I60, wiresI62'and 256, pressure switch 250, wires 25B and 260, motor 20,transformer 54, wires 262, and 264, and wires I66 and I46, and the oilburner will be placed in operation.

Pressure switch 250 is adapted to remain closed when the pressure in gasline is below a predetermined level, and to open when said gas pressurereaches a predetermined higher level. For example, if the operating gaspressure is two ounces, switch 250 may be set to open when the gaspressure is 1 /2 ounces or more, and to close when the gas pressuredrops to ounce.

When the oil burner is placed in operation, the primary coil oftransformer I94 is energized. Connected in series in the secondarycircuit of said transformer are a wire 26B, stack switch 252, Wire 266,outside thermostat 220, wire 210, main gas valve II 4, and wire 2'I2.Stack switch 252 is adapted to remain open when the furnace is cold, andto close when the stack temperature rises to some predetermined highertemperature. Thus when the oil burner is first placed in operation bythermostat 202 and transformer I94 is energized, and when the outsidetemperature is high enough to close outside thermostat 220, main gasvalve H4 can not open immediately since stack switch 252 is open. Afterthe oilburner has been in operation a few seconds, the stack temperaturewill become sufficiently high to close the stack switch 252, and thecircuit to main gas valve II 4 will be completed thereby. Said valve,thus opened, allows gas to flow through pipe 90 to operate dampercontrol 95 and to pass to burner tubes I4, where said gas will beignited by the oil burner. When the gas pressure reaches the levelrequired to open pressure switch 250, said switch will open, thusbreaking the circuit to the oil burner. Valve H4 is solenoid operatedand hence quick acting, while switch 250 is diaphragm operated and henceinherently slow operating. In this manner a sufficient time lapsesbetween the opening of valve I I4 and the opening of switch 250 toinsure that the gas burner will be ignited before the oil burner isturned off. Should the outdoor temperature fall below the setting of thethermostat 220, said thermostat will open, thus breaking the circuit togas valve H4 and closing said valve. Switch 250 will then close thecircuit to the oil burner, setting said oil burner in operation. Thusthe gas burner can operate only when the outside temperature is above apredetermined level, as determined by thermostat 220.

However, if, while the gas burners are operating, the pressure in thegas line at any time falls below the closing pressure of switch 250, orif the gas supply fails completely, switch 250 will immediately close toset the oil burner in operation.

If the gas pressure is adequate, but the gas for any reason fails toignite when valve H4 opens, bimetallic element 254 of stack switch 252will immediately begin to cool, and within a few seconds opens saidswitch, thereby breaking the circuit to valve I I4 and closing saidvalve. Switch 255 will then be closed, starting the oil burner inoperation. Stack switch 252 will normally open before stack switch I76of the primary burner control I92 functions to throw safety switch I68into the circuit and said safetyswitch rected.

While I have disclosed specific embodiments of my invention, it isapparent that many minor variations of construction and operation couldbe made without departing from the spirit of the invention, and it istherefore desired to be limited only by the scope of the appendedclaims.

What I claim as new and desire to protect by Letters Patent is:

1. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively to said burners, automatic means responsive to thetemperature of the space heated by said burners for setting said oilburner in operation to produce flame whenever heat is required, a" gasvalve controlling said supply means for said gas burner, means operableby the heat of combustion of said oil burner for opening said valve tosupply gas to said gas burner, said gas burner being positioned todeliver gas adjacent the delivery end of said oil burner so that saidgas is ignited by said oil burner flame, automatic means responsive tothe outdoor temperature for rendering said valve opening means operablonly when the outside atmosphere is above a predetermined temperature,and automatic time delay means operable by the pressure of the gas thussupplied to said gas burner to shut down said oil burner.

2, A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas-respectively to said burners, automatic means responsive to thetemperature of the space heated by said burners for setting said oilburner in operation to produce flame whenever heat is required, aquick-operating gas valve controlling said sup- "ply means for said gasburner, means operable by the heat of combustion of said oil burnerfor'opening said valve tosupply gas to said gas burner, said gas burnerbeing positioned to deliver gas adjacent the delivery end of said oilburner so that said gas is ignited by said oil burner flame, arelatively slow-operating pressure sensitive means operable by the gasthus supplied to said gas burner for shutting down said oil burner, andautomatic means responsive to the outdoor temperat'ure for renderingsaid valve operating means operable only when said outdoor temperatureis above a predetermined level.

3. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively'to said burners, automatic means responsive to thetemperature of the space heated bysaid burners for setting said oilburner in operation to produce flame whenever heat is required, a gasvalve controlling said supply means for said gas burner, means operableby the heat of combustion of said oil burner for opening said valve tosupply gas to said gas burner, said gas burner being positioned todeliver gas adjacent the delivery end of said oil burner so that saidgas is ignited by said oil burner flame, automatic means responsive tothe outdoor temperature and operable to render said valve opening meansoperable only when said outside temperature is above a falls below apredetermined lower level.

4. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for sup-plying fuel oiland gas respectively to said burners, automatic electrical meanscontrolled by an indoor thermostat disposed in the space heated by saidburners for setting said oil burner in operation to produce flamewhenever heat is required, an electrically operated quick-opening gasvalve whereby gas is supplied to said gas burner, automatic electricalmeans including a thermostatic stack switch operable by the heat ofcombustion of said oil burner to open said gas valve, said gas burnerbeing positioned to deliver gas adjacent the delivery end of said oilburner so that gas supplied to said gas burner is ignited bysaid oilburner flame, an outdoor thermostat connected in series with said gasvalve and said stack switch and adapted to render said valve openingmeans operable only when the outdoor temperature is above apredetermined level, and to close said gas valve whenever the outsidetemperature falls below said predetermined level, and a pressuresensitive time delay switch disposed between said gas valve and said gasburner, said pressure sensitive switch being adapted to break thecircuit to said oil burner whenever the gas pressure is above apredetermined high level, and to reestablish the circuit to said oilburner whenever said gas pressure falls below a predetermined level.

5. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively to said burners, a main valve controlling said gassupply, a gas pilot for said gas burner, a valve controlling the gassupply to said pilot, automatic means responsive to the temperature ofthe space heated by said burners for setting said oil burner inoperation to produce flame whenever heat is required, automatic meansresponsive to the outside temperature for opening said pilot valvewhenever said outside temperature is above a predetermined level andsaid oil burner is in operation, said gas pilot being positioned todeliver gas adjacent the delivery endof said oil burner whereby gassupplied to said pilot is ignited by said oil burner flame, and meansoperable by the flame of said pilot for shutting down said oil burnerand opening said main valve, whereby gas is supplied to said gas burnerand-ignited by said pilot.

6. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively to said burners, a main valve controlling said gassupply, a gas pilot for said gas burner, a valve controlling the gassupply to said pilot, automatic means responsive to the temperatureofthe space heated by said burners for setting said oil burner inoperation to produce flame whenever heat is required, automatic meansresponsive to the outside temperature for opening said pilot valvewhenever said outside temperature is above a predetermined level andsaid oil burner is in operation, said gas pilot being positioned todeliver gas adjacent the delivery end of said oil burner whereby gassupplied to said pilot is ignited by said oil burner flame, and

to close said pilot valve whenever said outside temperature falls belowsaid predetermined level, and means actuated by the flame of said pilotfor shutting down said oil burner and opening said main valve to supplygas to said gas burner, said flame actuated means bein dependent uponthe continued supply of gas at a predetermined pressure to said pilot,whereby when said pilot gas falls below said predetermined pressure,said main valve will be closed and said oil burner set in operation.

'7. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oiland. gas respectively to said burners, a main valve controlling said gassupply, a gas pilot for said gas burner, a valve controlling the gassupply to said pilot, automatic means responsive to the temperature ofthe space heated by said burners for setting said oil burner inoperation to produce flame whenever heat is required, automatic meansresponsive to the outside temperature for opening said pilot valvewhenever said outside temperature is above a predetermined level andsaid oil burner is in operation, said gas pilot being positioned todeliver gas adjacent the delivery end of said oil burner whereby gassupplied to said pilot is ignited by said oil burner flame, and to closesaid pilot valve whenever said outside temperature falls below saidpredetermined level, an auxiliary gas jet adapted to receive gas throughsaid pilot valve and positioned so that gas delivered thereto is ignitedby the primary pilot flame, and thermostatic means operable by the heatof said auxiliary jet to shut down said oil burner and open said mainvalve, whereby gas is supplied to said gas burner and ignited by saidpilot, said thermostatic means being operable whenever the flame of saidauxiliary jet is extinguished or reduced by failure of the gas supply orreduction of the gas supply below a predetermined pressure to close saidmain gas valve and set said oil'burner in operation.

8. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively to said burners, means controlled by a thermostatdisposed in the space to which heat is supplied by said burners forautomatically setting said oil burner in operation to produce an oilflame whenever heat is required, means rendered operable by the heat ofcombustion of said oil burner for shutting down said oil burner andsupplying gas to said gas burner, said last named means including a timedelay means whereby said oil burner is continued in operation for ashort time after the gas supply is initiated, said gas burner beingpositioned to deliver gas adjacent the delivery end of said oil burnerwhereby said gas is ignited by the oil flame, and automatic meansresponsive to the temperature of the outdoor atmosphere and operable torender said last named means inoperative to shut down said oil burnerand inoperative to supply gas to said burner when said outdooratmosphere falls below a predetermined temperature.

9. A combination gas and oil burner and control system thereforcomprising an oilburner, a gas burner, means for supplying fuel oil andgas respectively to said burners, means controlled by a thermostatdisposed in the space to which heat is supplied by said burners forautomatically setting said oil burner in operation to produce an oilflame whenever heat is required, means rendered operable by the heat ofcombustion of said oil burner for shutting down said oil burner andsupplying gas to said gas burner, said last named means including a timedelay means whereby said oil burner is continued in operation for ashort time after the gas supply is initiated, said gas burner beinpositioned to deliver gas adjacent the delivery end of said oil burnerwhereby said gas is ignited by the oil flame, and automatic meansresponsive to the pressure of the fuel gas supply and operable to rendersaid last named means inoperative to shut down said oil burner andinoperative to supply gas to said burner when said pressure falls belowa predetermined level.

10. A combination gas and oil burner and control system thereforcomprising an oil burner, a gas burner, means for supplying fuel oil andgas respectively to said burners, means controlled by a thermostatdisposed in the space to which heat is supplied by said burners forautomatically setting said oil burner in operation to produce an oilflame whenever heat is required, means rendered operable by the heat ofcombustion of said oil burner for shutting down said oil burner andsupplying gas to said gas burner, said last named means includin a timedelay means whereby said oil burner is continued in operation for ashort time after the gas supply is initiated, said gas burner beingpositioned to deliver gas adjacent the delivery end of said oil burnerwhereby said gas is ignited by the oil flame, and

automatic means responsive to the temperatureof the outdoor atmosphereand to the pressure of the fuel gas supply and operative to render saidlast named means inoperative to shut down said oil burner andinoperative to supply gas to said burner whenever either said outdoortemperature or said gas pressure falls below a predetermined level.

RICHARD H. SIEMON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,394,807 Blanchard Oct. 25, 19211,596,836 Hoff Aug. 17, 1926 1,722,253 Sherwood July 23, 1929 1,786,900Doherty Dec. 30, 1930 1,840,744 Scott Jan. 12, 1932 1,938,335 Hubbard etal Dec. 5, 1933 2,003,624 Bower June 4, 1935 2,065,533 Leahy Dec. 29,1936 2,081,091 Kuempel May 18, 1937 2,407,973 Beckstrom Sept. 24, 19462,451,661 Cochrane Oct. 19, 1948

